Wednesday, June 30, 2010

Some Miscellania

My PLA arrived last night. A beautiful 5 lb. roll of green filament. As a welcome surprise the folks at Ultimachine sent me two small sample rolls as well, one clear and one grey. I will use those for setting up the extruder and calibrating the machine.
I spent some time over the last couple of days on my next project, the powder printer. As I mentioned in an earlier post, I think that the laser cut bin setup created by Peter Jansen will make an excellent foundation to build on, although I will have to scale it up. I also reviewed all the blog entries that Alvaro Fogasa made on his work (good thing that I made a full copy since he has since lost everything in a computer crash).
I downloaded the latest version of sketchup which I will use to create models of all the parts. I plan on using modified versions of the Mendel parts wherever possible. That way I can create them on the Mendel and others will be able to pick up on the design. Luckily someone has already posted a sketchup file of all the Mendel RP parts so I have a great starting point.
The Mendel Y-axis carriage should work fine as the basis for the X-carriage for the printer. The repurposed printer carriage from a Lexmark Z12 printer will be mounted on it to privide the Y-axis movement with the printhead. I will redesign the mendel Y-carriage bearing mounts and use 5/16 barstock for the rails, just as the Mendel does.
I plan on mounting the whole shebang in a stock kitchen cabinet from Home Despot with locking wheels on the bottom so I can move it around. he storage space this will provide can be used for powder, bottles of binder, brushes, dust masks and all the other paraphenalia of printing.

Tuesday, June 29, 2010

Finally, an update with pictures!

I finally have a few shots of my progress. I have completed the frame and installed the x-axis. My only problem is that the z-screws seem to project too far below the machine and raise it up off the feet. I haven't checked yet to see if I measured something wrong or if this is due to using nuts that are thicker than intended. I expect the fix to be fairly straightforward though.

Sam, my assistant, guards my creation from evildoers

Here's a bit clearer shot of the whole machine.

My new motors arrived and I had no problems with installing the gears on these. Unfortunately I only have three of them so I will have to use one of my existing motors for the extruder.

Closeup of the z-axis 360 bearing and the x-axis motor.

The y-axis chassis is ready to go although I still have to do final adjustments on the bearings.

And, finally, a quick shot of the y-axis 360 bearings.

So, next steps are:

  • Resolve the issue with the z-screws.
  • Install the y-chassis and the bed.
  • Install the belts.
  • Move on to the electronics

I'm feeling pretty good at this point. the mechanical construction is almost complete. Since I bought pre-built electronics I am cautiously optimistic that they will work out of the box. That means that I could have a working Mendel within a week or so.

that is, if I can continue to work on it. Vacation is coming up and I need to put some serious time into getting my old '76 motorhome into shape for the trip. With a vehicle this old, that is only used once a year, there is always something to fix before we can head out so the Mendel may have to wait until we get back for the final touches.

I have ordered 5 lbs. of green PLA which should be here this week so I will be ready to build as soon as the machine is done. Then the real fun begins!

Tuesday, June 22, 2010

One Giant Leap for Powder Printer Hobbyists

Peter Jansen over at the reprap Builders Blog just posted a great article. He has been experimenting with a powder printer using selective laser sintering and has just published his design for a very inexpensive powder printer chassis. At this point it only has the two bins and the z-axis control hardware but it is a great start. His design could well become the de-facto standard for an open source powder printer. you would only have to figure out how the x and y hardware works and, if you are using a salvaged printer mechanism, only one of those.

The open source powder printer chassis

There is no scale in his article but I believe that the build area is quite small. He is, after all, experimenting so he doesn't want to build a large machine to prove his approach. Scaling up the design, though, should be fairly easy. I would like to see something with a build area that takes advantage of the capabilities of a salvaged printer mechanism. That is, either 8.5 x 11 or 8.5 x 14 inches.

Peter's geared drive mechanism for the bins

He uses a sqeegee rather than a roller to spread the layers of powder. I am not enough of an engineer to know whether this will work with all materials or not but is seems to me that it will have higher drag and might decrease the life of the motor.
His design has been posted at Thingiverse so we can all start right in on replicating and modifying it.
By the time I get Mendel working and start looking at powder printer construction I expect that this design will have have most of the bugs worked out. Since laser cutting is getting fairly cheap and very available I think that it should come together quickly except for the software.

Monday, June 14, 2010

Great Progress

I made considerable progress this weekend. Since the new parts go together so smoothly I was able to complete the x-axis and assemble all the parts for the z-axis and the y-axis. the y-axis parts are all installed on the squashed frog but I have not completed the alignment of the bearings yet.

I am now installing the electronics on the two electronics boards and then it will be time to begin the final frame construction. Since the boards that I bought from Techzone are smaller than the original design I am trying to figure out exactly where they mount and how. I should have that straightened out today.

The main problem that I still have to face is that I have have not yet managed to get the gears off of my stepper motors. I tried to drive the motor shaft out with a punch but it seems to be very firmly attached to the shaft. Even a couple of shots with a 2 pound steel mallet didn't budge it. I have resorted to attempting to cut one of them off with the Dremel. I wasn't able to finish the job last night so I will be back at it tonight or tomorrow. if I can't get the gears off, or if I damage the shaft in the process, I will just have to order new motors. At least they are not one of the more costly parts.

BTW - Nophead, who made my plastic parts, posted an excellent article on his blog today regarding an enclosure for the entire Mendel. It basically acts like a heated chamber and can also be used to contain and control fumes. It looks like a good idea to me but I would probably mount the electronics outside the box. I worry that the heat inside might shorten their life.

Friday, June 11, 2010

Construction begins.........Again!

I received the set of printed parts from Nophead last night.

It took me two weeks of spare time and hours of drilling, grinding and sanding to get all the subassemblies for the x-axis built using the cast parts. Even then, they didn't align properly when it came to installing them on the rails. With the properly printed parts I was able to build all of the same subassemblies in 2 hours and all of the holes for the rails align so they should go together just fine. I hope to have the whole x-axis together tonight if I get some free time. Since it has been raining here for days that seems likely.

Thursday, June 3, 2010

A New Start

Well, I won the auction so I now have a new set of parts coming. They were pretty expensive but at least they will allow me to actually assemble a working Mendel. Here's the Ebay Pic:

So, I will have to wait a week or so for them to arrive and then the build should proceed in a fairly straightforward manner.

In the meantime I will try to get the old gears off my motors and install the new ones. I can also finish the extruder build, except for the HeatCore piece.

Tuesday, June 1, 2010

A Long Overdue Update

Things have stalled at the moment. I have been unable to get the various components for the x-axis to align properly on the rails. the holes are just not in the right place (or rather, are differently spaced on different components so the rails are never parallel). I have just about given up on the molded parts and I have actually bid on another set of properly repraped parts on Ebay. That auction closes tomorrow and I would then have to wait for delivery before starting my assembly again. If I win it I will also get another set of geared extruder parts so I can build a backup extruder. Since this set is manufactured by Nophead, definitely a respected name on the forums, I can be sure that they have been made properly and will fit together as they should.

I received the "Adrian's Extruder" parts and I have started assembling them. I first gathered all my parts together and discovered that I had not purchased a thermosensor so I sent a quick order to Makergear for a couple, as well as some insulating fabric. I need a couple of 55mm bolts but the longest ones I have are 45mm and won't fit. I am going to cut a couple of pieces of the 4mm threaded rod that I bought and put nuts on both ends. I had to buy 3 feet of the stuff so I have lots to play with. The geared brass insert was the toughest thing to find. I finally located a hobbyshop in England that had them and was also willing to ship overseas so I bought 10 of them and they arrived last night. They are not threaded on the inside but they have a grub screw that will dig into the threads on the shaft and hold them in place.

I also started to assemble the removable HeatCore heater from Makergear that I bought but ran into a problem. After applying the ceramic paste over the nichrome wire they recommend hooking the unit up to the Mendel electronics to cure the paste at high temp. I don't have my electronics hooked up yet so this will have to wait. I thought about trying to cure it in the oven but I don't want to experiment at this point and I have lots of time before I will need a functioning extruder anyway.

Last week I was able to meet Mike (Dissidence) in person. He has a lot more electronic knowledge than I do and is creating his own design from scratch. It's great to have another raprapper within driving distance. We are setting up a forum for Saskatchewan on the Reprap site so we can start to gather other, like-minded, builders together. I look at this in a completely selfish light... the more local people who are interested and working on these machines, the more likely that I can find someone to help me with my inevitable problems.

So come one, come all!